Leather substitute



Patented J... 17,1923.

3 UNITED STATES PATENT OFFICE.

JOHN D. uenumwnr AND areas. a. NOLLAU, or mawnunen, Nnw YORK, nssrenons r 1:. I. no PON'I. nn nnmouns a COMPANY, or WILMINGTON, DELAWARE, A son- POBA'IION OF DELAWARE.

nan-man sunsrrrurn.

Application filed June 24, 1926. Serial 110. 118,164.

This invention relates to leather substitute of the cellulose ester, e. g. pyroxylin, coated type. Although the substitute of the present invention is not restricted .in its use to 5 the bookbinding art, it finds particularly advantageous use in that art, and therefore the invention is described with more particular reference to that art.

Pyroxylin coated leather substitute, such as fabrikoid, has, as is Well-known, found a lar e field of use in the bookbinding art; but there are certain respects in which 1mprovement is highly desirable, in order to make the leather substitute :is satisfactory as possible and overcome certain difiiculties that have become apparent in the use of the material :--In handling and inspecting books bound in leather substitute one fre uently finds that the paper end leaf has ecome detached from the leather substitute. This detachment takes place along the edges, of the end leaf where they are stuck to the margin of the substitute where the substitute is carried over the edges of the-stiffen- 5 ing sheet or board of the cover (forming the turn-in) and fastened to the inside surface of the board. To the observer such a loosening of the end leaf from the substitute suggests careless work on the part of the bookbinder; but such is not the fact. The difiiculty is that the p roxylin surface of the substituteit will he noted that it. is this surface that is exposed on the inside of the cover at the turn-in and to which the end leaf is attached-is of such character that the glue or other adhesive that is used for connecting the end leaf and the turn-in will not properly spread on and' permanently adhere to the turn-in.

We have now devised a leather substitute which, although it-has the desired non-sticky, waterproof surface and all-pyroxylin leather substitute film, will properly take glue and other similar solutions and give a perma- 5 nent joinin with any material attached thereto. It is the major object of the invention to provide such a substitute.

We have found, upon-careful investigation, that the poor adhesion is due to the so high interfacial tension existing between the pyroxylin and the adhesive solution, or the medium which carries the adhesive proper, e. g. the water which carries the glue. hat is to say, the poor adhesion is due asto the glue-solution, or the water, not propducer to the pyroxylin surface. This reerly wetting the pyroxylin surface. U on further investigation we have found t at the d fiiculty may be overcome by. the apphcat on of a proper interfacial tension reducer -is casein. "It is to be understood that the casein is not used in the capacity of an adheslve or of a water-proofing agent; it

IS used to facilitate the proper-application and adhesion of the usual adhesive.

In the accompanying drawin Figure 1 1s a conventional.cross-sectiona view df a leather substitute embodying the present inventlon, and Figure 2 is. a fragmental perspective-view of a bookbinding, illustrating the use of the present material.

Referring now to the drawing, and particularlg to Figure 1, the present leather substltute comprises the woven fabric back 1, the pyroxylin film 2, and, on the surface 7 of the pyroxylin film, the casein 3. (It w ll be understood that no effort is made in the drawing to indicate relative thicknesses with accuracy.)

The'material may be made as follows Any suitable woven fabric base is coated, as 1n a standard coating machine, with a pyroxylin of substantial thickness, thereby to give a pro er leather-substitute surfaceas distin ed from' merely sizing the goods. hus', there may be applied three coats of the following coating composition (parts by weight):

Cellulosenitrates a i. 16. I Caster oi 26. Dry

igment of any desired type as car on black ..../10. Benz l 67.8 Alcohol 27.9 Ethyl acetate 27.9

Each coat or sub-film is dried after depositing and before the application of the next, and the a gregate ultimate coat or film is" desirably rom .002 to .004 inch thick.

After the fina'ii pyroxylin sub-film has dried, the casein is applied. This may be done in any desired way as with a coatin machine, dryin the casein coat (and ling the volati e ammonia) With'the ai of steam heated coils. As many coats as is necessary to give a finish of the desired thickness, say .00025 to .001 inch, may be applied, drying after each coat, o'ne coat bemg generally sufiicient. The thin casein 1m coat effects no change in the substitute with re ard to appearance, wearing qualities ability to be embossed, rolled etc. The.

compositionmay desirably be as follows In the above composition, for the dispersing agent, ammonia, others may be substituted, as various alkaline substances such as borax or sodium or potassium hydroxide, or certain acids, such as citric acid. Ammonium hydroxide, however, is believed the most desirable since, in dryin the ammonia is expelled with no alkai remaining; and alkali under certain circumstances might be injurious to the pyroxylin film. For the softening agent, glycerine, others may be used, such as various other polyhydric alcohols, for example ethylene glycol. Ethylene glycol has, indeed, merit, but whereas 10 and 12.5 percent. of glycerine (based on the weight of the whole composition) is highly satisfactory, even about 25% of ethylene glycol is less so. While, a polymerizing a ent for the casein, for example formalde yde, may be used, its use has not been found of material advantage. 'For the coloring matter in the composition there may be used any one giving the desired color, for instance, a suitable dye or pigment, e. g. carbon black. As indicated, the concentration of the color component will vary considerably, depending on the shade and the material, but approximately 0.5

' percent (based on the total weight of the (liquid) composition) is generally satisfactor 1 Figure 2 of the drawing there is shown a portion of a book cover illustrating the use of leather substitute in binding and indicating the particular significance of the present material. In this fi re the board of he cover is shown at 4, and the leather su stitute at S. The substitute, when applied, has its pyroxylin surface 2 exposed on the outsidg of the cover, and when the substitute is turned in over the ed e of the board, as indicated at 5, this sur ace 2 is still the exposed one. Thus, when the back leaf 6 is fastened to the board 4, with paste or glue, it becomes necessary to fasten it to the pyro lin surface of the leather substitute. Wit material of the resent invention, its pyroxylin surface eing covered with the interfacial tension reducer, this can be properly and permanently done.

Returning now to the interfacial tension red e as stated casein has een f und the most suitable for the purpose, the desideratum being a material that not only has the primary propertg of reducing the interfacial tension between the pyroxylin and the usual adhesives, or the organic hydroxylic compounds such as water and alcohol, used assolvents for such adhesives, e. g. paste, glue, gelatin, shellac and so on causing the ad: hesive. (solution) to wet the and spread properly thereon,- at a so is insoluble in water and not sticky, will, in -solution, full I spread upon and wet the pyroxylin when the material is subjected to the embossing press, and so on. With the present substitute, glues, pastes, gelatin solutions, and so on, roperly sprea on the surface of the substitute and wet the same over the entire surface thereof, so that when the material to be fastened to the substitute is applied thereto-complete facial connection and permanent anchorage between the substitute and the material is obtained.

To mention further advantages of the material, also particularly apparentin the bookbinding art -In applying the gold, or other leaf, to leather substitute bindings of the usual type difliculty has been experienced in obtaining proper adherence of the leaf to the pyroxylin film. With the usual t e of pyroxylin-surface leather substitute it is necessary, preparatory to the stamping of gold leaf, to wash the surface with a size consistyro lin film m, and will cause no difficulties ing usually of an aqueous-borax-shellac, or

an alcohol shellac, composition, to prepare the surface and endeavor to obtain proper adherence of the leaf. Such application of the size is, however, unsatisfactory as the size fails to spread properly or wet the surface-a condition comparable to that obsurface. This behavior is the direct result of the high interfacial tension existing between water or alcohol and the leather substitute. A

Becauseof the above considerations, it is customaryto resort to the use of a special alcohol wash preparatory to the application of the shellac size. Not only does such a practice mean an additional operation in the bindery, but under certain conditions special size compositions prepared for leather substitute material behave'quite unsatisfac-" torily. With the present material the use of the ordinary shellac size is made entirely .possible', without-the use of any i the Speserved when mercury is poured upon a glass lll III

- quires about three days to,dry, whereas the present material with colored ink, the ordi nary inks employed with leather may be employed, it being tumecessary to use the special ink heretofore necessar in stamping pyroxylin-surfaced goods. stantial' advantage sincethe special ink reregular inks require but about twelve hours. While in the foregoing description the interfacial-tension-reducing coat has-been described as applied to a pyroxylin coat con-' taining oil it will be understood that its efficiency is not dependent upon whether or not the pyroxylin coat containsoil, the re.- ducer overcoming a difiiculty existing with the pyroxylin coat whether or not it contains oil. Furthermore,,the invention is applicable to leather substitutes havin films of cellulose esters other than nitroce lulose, as cellulose acetate, the casein overcoming the difficult of non-wetting, and so on, as heretofore escribed. o

Although the material to be attached to the leather substitute has, for definiteness, been described as paper, i. e. the back sheet of a binding, it will be understood that theaction of the interfacial tension reducer is not dependent on the articular material to be attached to the leat er si1bstitute,-as the T is is a sub-- paper may be glazed or unglazed, or some other material.

While casein has been particularly mentioned, and is preferred, other materials comparable to casein, in being satisfactory inter-facial tensionreducers, water insoluble, non-sticky, and capable, when used alone without admixture with pyroxylin, of adhering pro erly to pyroxylin, and fully spread ng t ereon, may be used.

We claim:

1. A leather substitute com rising a fabric backing, a pyroxylin film o leather-substitute type, and a surface film comprising casein.

2. A leather substitute com rising a fabric backing, a pyrox lin film o leather-substitute type,'a sur ace film of casein, and a softener therefor.

3. A leather substitute comprising afabric backing, a pyroxylin film comprising-a plu-. rality of substantial-sub-films, and, directly on the pyroxylin film, a film of casein.

4. A leather substitute comprising a textile fabric backing, a pyroxylin film of leather-substitute 'type, and a waterproof, non-sticky, flexible, pyroxylin-free surface film comprising, as an interfacial tension reducer, casein.

In testimony whereof we aflix our signatures.

JOHN D. MGBURNEY. EDGAR H. NOLLAU. 

